How about this team for starters? Sand-stream based to an extent.

 Tyranitar@Assault Vest
 Careful nature 252 HP 252 Sp.Def 4 Attack

 Earthquake
 Crunch
 Stone Edge
 Pursuit


 Pretty insane this generation as far as sp.def walling goes, this reaches near 700 I believe.
 Give it durability which is important to refresh sandstorm.

 Mawile@Mawilite
 Intimidate
 Adamant 252 HP 252 Atk 4def

 Play Rough
 Iron Head
 Sucker Punch
 Brick Break/Fire Fang/Substitute

 Your mega-evolution, setup-free core. This fucker hurts a lot.

 Excadrill@Life Orb
 Sand Rush
 Adamant 252 Attack 252 Speed 4 HP

 Swords Dance
 Earthquake
 Rock Slide
 X-Scissor/Poison Jab/Shadow Claw/Rapid Spin

 Your core set-up sweeper. This guy's insane, you get one swords dance off and almost everything in the game is fucked.
 Obvious downside is priority, this guy should be pulled out after its counters have been dealt with to end the game.

 * side note - he's very sandstorm reliant. playing him well would be key to your victory or loss. you have 4 actual turns,  3 excluding the one you SD in, to do your damage. use them well.

 Next I'd say go for a Salamence. He has key fighting, fire and water resist and ground immunity.

 Just copy the top set at Smogon, there aren't that many ways to play it.
 I opt for Scarf mence because you already have a Pokemon that's set-up reliant [though you CAN have 2] and he's a very  effective revenge killer that's independent of Sandstorm, unlike Excadrill.

 Azumarill@Choice Band
 Huge Power
 Adamant 252 HP 252 Attack 4 def

 Waterfall
 Aqua Jet
 Play Rough
 Super Power

 Hits like a truck, can easily find switches because of fighting, water and fire resists.
 Easy revenge killer for those fast threats like Blaziken, other Excadrills and other fragile mons.

 THAT said, you CAN try a belly drum set, but it's just a huge risk. Mostly you need the terrain to be clear of counters.

 Togekiss@Leftovers
 Serene Grace
 Bold 252 HP 252 Def 4 Sp.Def

 Wish
 Thunder Wave
 Air Slash
 Fairy attack/toxic/protect/etc

 Togekiss works as team support, he dishes out thunder wave [which is key with slow Pokemon like T-Tar, Mawile, and Azumarill .
 He can hand out wish and has big physical bulk along with, again, key ground and fighting resist.

 Things to note:
 Yeah, you have 3 fairy types, but since 2 are neutral to steel, and 1 is immune to poison, it really doesn't matter, it's  just an added bonus resist to fighting.

 This was made off the top of my head using the idea of sandstorm, but it's by no means what you HAVE to play, just a  general idea.

 If you like any sets in particular, you can just copy them and transfer them to other teams.
 The only one here who is really reliant on the other members is Excadrill.

 If there's other mons you want me to incorporate say so.

 I may have missed obvious synergy problems/counters so it's by no means perfect.